Openrail and V-bearings

Does anyone have any experience of Openrail and V-bearings?

How would they compare in terms of accuracy vs supported rail or profile?

Seems remarkably cheap, even with all the little extras included. I'm normally incredibly wary of any solution that comes in significantly cheaper than the alternatives, but everyonce in a while, I am pleasantly suprised.

Many thanks in advance for any replies.

P.s. if you've never used it but have an opinion, please still speak up.

Worked with these in the past and still have them on some machines at work. They are fine for general machine motion as long as you dont need to be super accurate or need a really smooth ride. They wont give a really smooth ride if there is any crap on the rails and will tend to bounce over it. This isnt a problem for profiling but will be for a router or mill.